Lithographic plate graining device



June 18, 1935. R, FRn-SCHE 2,005,654

LITHOGRAPHIC PLATE GRAINING DEVICE Filed Jan. 9, 1934 2 Sheets-Sheet 1mi 'l Y INVENTOR VRudolf' Esche ATTORNEYS June 18, 1935. R FRWSCHE2,005,654

LITHOGRAPHIC PLATE GRAINING DEVICE Filed Jan. 9, 1934 2 Sheets-Sheet 2INVENT druml, or for any other purpose.

Patented June 18, 1.935

UNITED STATES PATENT OFFICE Application January 9,

2 Claims.

This invention relates to lithographic plate graining and has for anobject to provide a construction wherein a plate may be grained in aminimum time.

Another object of the invention is to provide a device for graininglithographic plates wherein the graining is uniform and deeper than nowin common use.

An additional object is to provide a graining machine for graininglithographic plates wherein the graining is formed with roundeddepressions and smooth protuberances instead of the hooked form as nowin common use.

A still further object, more specically, is to provide a grainingmachinefor graining lithographic plates wherein sand and water is thrownagainst the plate by one or more agitating and impelling blades whilethe plate is moving.

In the accompanying drawings- Figure 1 is a longitudinal'verticalsectional view through a graining machine disclosing an embodiment ofthe invention;

Figure 2 is an enlarged fragmentary vview partly in section,illustrating certain clamping means embodying certain features of theinvention;

Figure 3 is a sectional view through Figure 1 on the line 3 3, the samebeing on a reduced scale;

Figure 4 is a greatly enlarged view through a lithographic plate afterthe same has been grained according to the present invention;

Figure 5 is a view similar to the lower part of Figure 1, except that itillustrates a modified construction wherein only one agitating andimpelling structure is used.

Referring to the accompanying drawings by numeral, I indicates a frameof any desired kind, as for instance, a metal frame formed of angle ironetc., riveted or otherwise rigidly secured together. The casing 2 ishingedly connected at 3 to the frame I and is provided with a catch 4for normally holding the same closed. AThe cover 5 is hingedly connectedat 6 to the casing 2 whereby ready access may be had to the upper partof the casing at any time. By reason of the hinge connection 3 theentire casing may be swung to one side when it is desired toA insert orremove the The drum 'I is preferably connected with shaft 8 journaled in'suitable members 9" carried by the side walls of the casing 2, wherebywhenever the casing 2 is swung to the dotted line position shown inFigure 1, the drum will be swung out of the hopper I0. The hopper I iswatertight except that it is completely open at the top and at thebottom and has a discharge passageway I I normally closed by 1934,Serial No. 705,945

the cap I2, which may be held in place by threads or other desiredmeans. The hopper I0 accommodates about half the drum I and merges intoan almost rectangular section I3 which is divided by a partition I4having any desired number of apertures I so that there will be freecommunication between the respective compartments I6 continually meshingso that when power is ap- I plied to the pulley 2I the power will betransmitted to both of the impellers I8 so that they will operate at acomparatively high rate of speed.

It will be evident from Figure 1 that there is provided a quantity ofsand 23 in each of the compartments IB and I 1, and also a supply ofwater, whereby when the impellers are functioning the water and sandwill be forced upwardly in the form of sprays 24 and 25, said water andsand striking the lithographic plate 26 and forming graining thereon.'I'his graining is shown greatly enlarged in Figure 4. From this gure itwill be observed that', there are provided a number of depressions 2lfor retaining the water when the plate is in use. Naturally there willbe provided between the depressions 21 a number of raised portions 28which are rounded more or less. Thedepressions 2l are really rounddepressions aring from the bottom upwardly. The illustration shown inFigure 4 would be a perfect or ideal formation of graining shown on alarge scale. In the regular performance of the machine, however, thedepressions 2l are seldom formed so accurately but they present inappearance substantially the form shown in Figure 4,

namely, rounded protuberances in the same plane with depressions forholding water when the plate is in use. The sand striking the plate isshown in Figure 1 to produce the depressions but does not cut away theplate. The use of water and sand causes the sand to make merely dentseach time it strikes and then becomes inoperative until one of theblades of one of the impellers forces the same violently against theplate a second time.

The drum 1 may be solid'or hollow and formed of any desired material,though ordinarily it is made solid from suitable material, for'instance, wood. This drum carries the axle or shaft 8 which is journaledin suitable bearings 9. This shaft is rigidly secured to drum 1 so as torotate therewith. The pulley 29 is secured to shaft 8 and receives powerfrom any suitable source whereby it is rotated very slowly, while theimpellers I8 are rotated at comparatively high speed, for instance, fromabout seven hundred revolutions per minute to eighteen hundredrevolutions per minute.

As shown in Fig. 1 the plate 26 is clamped by suitable clamps 30 and 3lto the drum.1 and extends slightly over half way around the drum. Whenthe machine is started in operation the clamp 30 is near the spray 24and as the drum 1 moves slowly in the direction of the arrow 32 (Fig. 1)the action of the water and sand continues. Preferably the drum moves ata rate so that the entire plate 26 will be grained in from ten to twentyminutes according to the speed thereof and the speed of the impellersI8. If the impellers I8 are running at an extra high rate of speed, forinstance, as high as would be practicable, the plate 28 might be causedto move at a rate whereby the graining could take place in a short time,for instance, about ten minutes. If the impellers are running at a slowrate of speed the drum 1 could also be rotated at a slower speed,namely, so that the graining may take place in about twenty minutes.After the parts are startedin operation the action is automatic. If forany reason the operator should forget to stop the drum 1 and theimpellers I8 when the graining has been completed, no damage will bedone as the drum will merely continue to rotate and as it passes sprays24 and 25 will be again bombarded with sand and water, but this will notinjure the plate but .the action will merely be unnecessary.

The clamping members 30 and 3I as shown in Fig. l are shown more indetail in. Figs. 2 and 3. From these figures it will be observed thatthe drum Tis provided with metallic rings 33 and 34 rigidly securedthereto in any desired manner and projecting a short distancetherebeyond. A

clamping bar 35 (Fig. 3) extends for the full length of the drum 1 andis provided with hooks 36- and 31 at the respective ends, said hookstting ove'r the'extending portions of rings 33 and 34. A set screw 38 iscarried by the bar 35 at the ends (Fig. 2), said set screws beingadapted to be screwed tightly against the rings so that the hooks willbe pressed against the under surface of the rings and thereby bar 35held rigidly in place. 'I'his bar carries a number of adjusting screws39 which are rotatably connected with rplates 40 so as to move saidplates toward and from the bar 35. Plate 40 is provided with a pair ofpins 4| slidably fitting into the respective apertures 42 in bar 35.From this structure it will be observed that whenever the end of alitho- 40 of clamp 30, the end may be readily clamped firmly to drum 1by screwingl down on the set screws 39. The opposite clamp 3| isoperated in the same way whereby the lithographic plate is normallyclamped in place at each of its longitudinal edges and fits snuglyagainst the drum 1 so that there will be a comparatively rigid backingfor the plate whereby the bombardment of the sprays 24 and 25 willproduce the desired graining action. After the plate has been grainedthe parts are stopped and the cover 5 swung to an open position, afterwhich the plate may be disengaged from the clamps 30 and 3l and removed.If desired, a second plate could be mounted in place and the devicecaused to repeat the same operation on the second plate.

In Figure 1 two impellers have been shown for bombarding the plate to begrained, but it will be evident that ra greater or less number ofimpellers might be used without departing from the spirit of theinvention. As shown in Figure 5 a single impeller 43 is disclosed. Thisimpeller is preferably of the same shape as the impellers I8 andfunctions exactly as the impellers I8, namely, to scoop up some of thesand in the bucket 44 and some of the water and discharge them with someappreciable force in the spray against the plate 26 which is beinggrained. As there is only one bombarding spray 45 in this form of theinvention the drum 1 naturally moves at a slower rate of speed, but thesame results are eventually secured. It will be noted that the blades ofthe impellers I8 and 43 rotate from a central hopperI for a certaindistance and then curve in the direction of movement, whereby smallbuckets are formed which scoop up the water and sand and then provide animpelling construction for projecting the sand and water thru the air ina spray. Other blades of different shapes could be used but this shapehas been found desirable in that it limitsthe area of the spray 45 and,consequently, by causing the spray to be constant andthe speed of thedrum 1 to be constant, will produce a very fine and uniformly grainedsurface.

In the course of time the sand mayfbecome broken up or dirty and whenthis occurs, or whenever desired, it may be removed as well as the Waterthrough the discharge opening II by merely removing the cap I2.Y Watermay be pumped in at the top for flushing out the device and then cap I2replaced, then a supply of clean sand is added and the desired quantityof Water which is preferably maintained at a level up to the hub of therespective impellers. The level of sand is always such that eachimpeller blade is adapted to scoop up sand in small quantities each timeit reaches the lowermost point.

I claim:

1. A device for graining lithographie plates, comprising a rotatabledrum, a pair of clamps for clamping a plate onto the drum, each of theclamps including a supporting bar, a plurality of clamping blocks, meanscarried by the clamping blocks extending loosely into said bar so as tobe guided in their movement toward and from said drum, and a clampingscrew for each block, said screws being carried by said bar and adaptedto cause the clamping blocks to press said plate against said drumtightly when moved in one direction, and to move the blocks away fromthe drum when rotated in the opposite direction, and means forbombarding the plate to be grained as the drum moves.

2. In a graining machine for graining lithographic plates, a drumagainst which a plate is adapted to be fitted ilatwise, a ring securedto said drum at each end, said rings projecting beyond the drum so as topresent end anges, a clamping bar extending longitudinally across thedrum, said bar at the ends having hooks adapted to be hooked over saidflanges, means for clamping said hooks against said flanges, and aplurality of plate clamping means carried by said bar. z

RUDOLF FRITSCHE.

